The Move to Dynamic Glass

Architects, building owners, and occupants are embracing next-generation windows for improved sustainability

It's no secret that architects love glass. The material is dramatic, sustainable, and bridges the interior of a building to its environment. Dynamic glass, which tints electronically in response to outside conditions, is proving itself superior to static glass. With the intelligence to provide optimum natural light and comfort regardless of exterior conditions or time of year, dynamic glass has far-reaching implications for building design, ongoing building performance, and occupant experience.

This is an important consideration in light of the fact that windows are commonly regarded as one of the least energy-efficient building components, responsible for up to 40 percent of the total heating, cooling, and lighting consumption. By making fenestration a responsive façade solution for solar control, dynamic glass has become a key component of high-performing buildings. This article will describe how dynamic glass behaves, its benefits for architects, building managers and users, and present studies and real-world examples of its use. Also covered will be how the technology is being increasingly referenced in energy codes and sustainability rating systems such as the U.S. Green Building Council's Leadership in Environmental and Energy Design (LEED) Version 4.

Dynamic Glass—What Is It?

Dynamic glass switches between clear and tinted states on demand, providing glare and heat control while offering continuously unobstructed views. The system can function autonomously or be controlled on demand, enabling a user to tint or clear the glass according to preference. In automated mode, the system will automatically tint or clear the glass, adapting to environmental conditions.

Dynamic glass switches between clear and tinted states on demand, providing glare and heat control while offering unobstructed views. Photo courtesy of View Inc.

Advanced dynamic glass can deliver separate tint levels, corresponding to less than 4, 20, and more than 60 percent visible light transmittance (Tvis) with other tint levels available as required. In its fully tinted state, building occupants can block out heat and manage glare while still seeing through the glass for an unobstructed view of the outside world.

The technology allows for control of individual windows or coordinated groups of windows. With a grouping capability, zones can be created to tailor the behavior of the glass for spaces with different uses or even within a single façade for optimal daylighting. For example, in a curtain wall design, the top course of vision glass could be set to 20 percent Tvis, admitting light for daylighting purposes, while the remaining eye-level glass can be set for a darker tint to decrease glare.

With this zoning capability, dynamic glass control can be integrated into building management systems, or be controlled from a tablet or smart phone.

Technologies

Not all dynamic glass functions the same way. Examples of technologies that enable smart windows include electrochromic (EC), thermochromic, photochromic, liquid crystal (LC) and suspended particle devices (SPD). Thermochromic and photochromic technologies change their properties based on ambient temperature and ambient light levels respectively. They are commonly termed “passive” dynamic technologies. EC, LC and SPD technologies have the advantage of active electronic control of glass performance, enabling truly intelligent controls that can be integrated with occupant schedules, lighting levels, or algorithms to increase building energy efficiency. Both LC and SPD require continuous high-voltage AC power to operate, and their failure mode is to a dark state. EC technology has the advantage of using low voltage, has very low energy consumption, and has a power off mode that is neutral or clear.

For EC glass, multiple thin layers of metal oxide form the electrochromic component on the inside of the glass. In the absence of a voltage, the metal oxide film is completely transparent. With the application of a 5-volt electrical charge, the ions in EC glass move between layers, changing its properties and tinting the glass. The darker the tint, the more solar radiation and glare are rejected, resulting in temperature and energy control. The coating itself has the low emissivity benefits similar to traditional low-e glass, enhancing the thermal performance when combined into a dual pane insulting glass unit. The application of EC technology to windows can substantially reduce the energy consumption of buildings by reducing cooling and heating loads as well as the demand for electric lighting. Among the aforementioned smart window technologies, EC is the only one to have passed the ASTM standard for accelerated environmental durability, which designates a 50-year service life.

The application of EC technology to windows can substantially reduce the energy consumption of buildings by reducing cooling and heating loads as well as the demand for electric lighting. Photo courtesy of View Inc.

Intelligence

Since dynamic glass is intelligent and can change, it can adjust to the outside world, to provide optimum natural light and comfort, no matter what the conditions or time of year. Photo courtesy of View Inc.

While the glass provides the tint, the system makes it intelligent. Predictive intelligence foresees the sun's movement and automatically adjusts each window's tint to anticipate the sun's solar load. The same intelligence then adjusts the tint level according to location, space type, weather, and user preference. Each window has local intelligence and knows its unique position, orientation, and condition. As a result, the intelligence function seamlessly manages direct glare on occupants while maintaining the architect's intended views. As inputs to the intelligence function, several project parameters are required, including the following:

• Building location and orientation sunpath

• Exterior building characteristics

• Interior space design

• Maximum heat load allowed

• Sensors

In practical terms, the dynamic glass manufacturer collects the required project parameters from blueprints and site visits, building up a database for each project. A building's longitude and latitude will be noted as will sun location coordinates and sun radiation year-round. Zoning will be taken into account as well as window measurements, interior measurements, and the building's maximum heat loads and sensor inputs.

Intelligence computes in the following three ways:

Glare control. Intelligence calculates the angle of the sun and determines if there is glare on occupants, and tints the window down if necessary.

Heat load control. The heat load of the space is managed to be lower than peak solar heat gain design load and associated HVAC design, and daylight is maximized. Based on maximum radiation for a particular façade for a specific time and day, intelligence will determine the necessary tint state to keep heat gain below peak/maximum. As shown in the accompanying figure (see the online version of this course), Max Inside Radiation = Max sun radiation * SHGC of glass. Intelligence tints glass down as needed to keep heat generated by the sun in the room below the design maximum. With this control, the building's peak load will be reduced compared to a baseline design using static glass. The dynamic glass design therefore requires a smaller building HVAC system.

Image courtesy of View Inc.

Daylight control. Based on actual environmental conditions, the intelligence function adjusts the tint level to achieve maximum amount of daylight. The inside radiation equals the outside radiation * SHGC of glass. Based on actual environmental conditions, the tint level will be adjusted to achieve the maximum amount of daylight.

Image courtesy of View Inc.

System Architecture

A focus on simplification and performance has driven a major rethinking of the dynamic glass electronic system architecture. In many cases, traditional complex wiring approaches have been replaced by a single line or cable, similar to a LAN network, to facilitate routing and reduce install complexity. Factory pre-terminated wiring with threaded connectors cuts labor time and adds to long-term reliability. Window control has been moved to intelligent nodes close to the window to optimize tint uniformity and allow maximum zone control flexibility, user control, and ease of future reconfiguration. Intelligence at each point, from the insulated glass unit (IGU) back to the user interface, facilitates maximum user flexibility and central or individual control.

Architects can specify large glass units active edge-to-edge without internal conductors that interrupt the view. Photo courtesy of View Inc.

Energy Benefits

Dynamic glass contributes to thermal management of a building in two major ways:

Peak cooling load reduction. Dynamic glass can tint during peak cooling demand periods, thereby blocking more than 90 percent of solar radiation and resulting in a reduction of peak cooling required. This results in reduced HVAC equipment sizing as well as system simplicity when compared to traditional glazing solutions.

Annual energy savings. Due to its interactive nature, dynamic glass reduces overall HVAC energy consumption and costs by limiting unwanted heat gain in summer but allowing beneficial passive heat gain in winter. Intermediate states convey additional benefits by saving lighting energy, thus allowing for optimal daylighting.

These statements are based on whole-building energy simulations developed to compare the energy use of current low-E glazing and high-performance dynamic glass. A typical 20-story high-rise office building with high performance low-E glass was modeled against a building with dynamic glass. The analysis was conducted across five U.S. cities in different ASHRAE climate zones. The window-to-wall ratio modeled was 50 percent, which is typical for high-rise buildings. With all other aspects held constant, the difference in energy performance was a direct result of the performance of the glass. Averaged across these typical climates, use of dynamic glass reduces lighting and HVAC electricity (space cooling, ventilation fans, pumps) consumption by 20 percent. The savings in lighting energy is attributed to the intermediate state features of dynamic glass and dimmable lighting.

Compared to high-performance low-E glazing, the dynamic glass modeled reduced the building's cooling peak load by 23 percent which in turn results in a reduction of HVAC system size (reduced cooling tons, fan, shaft and duct size, chiller, terminal units, diffusers, pumps, and water circulation) required to meet the peak load in the building. Beyond the opportunity of straightforward equipment cost reductions, the reduced peak cooling loads also offer a chance to use alternate cooling systems. Options such as radiant chilled ceilings and displacement ventilation can further reduce capital costs, lower maintenance or add greater design flexibility. Peak load reduction can decrease and possibly eliminate peak demand utility charges as well. Reducing peak loads for the building allows for the negotiation of a lower peak demand structure and passes significant operating cost savings to the owners of such facilities.

In a similar analysis, a typical 4-story low-rise, 40 percent window-to-wall ratio office building with high-performance low-E glass was modeled against a building with dynamic glass. The low-E glass building contained a shading overhang on the southern façade, which was eliminated for the dynamic glass building. Otherwise, the two buildings were identical. On average, use of dynamic glass was found to reduce lighting and HVAC electricity (space cooling, ventilation fans, pumps) consumption by 14 percent, and cooling peak load by 8 percent. Even in smaller buildings with less fenestration, dynamic glass has substantial energy and design benefits.

Image courtesy of View Inc.

Dynamic Glass—The Beneficiaries

The advantages of dynamic glass extend to three main groups—architects, building managers, and occupants.

Building Designers

Dynamic glass offers greater freedom, enabling architects to use more glass with confidence in striking design solutions while still meeting the performance objectives of building energy codes and standards.

With the use of dynamic glass, shading devices, both external and internal, can be reduced or eliminated. Devices like external blinds and louvers block direct views. When required, dynamic glass can be deployed in its fully tinted state, taking advantage of its low shading coefficient thereby minimizing solar gains and essentially obviating the need for external shades. This not only reduces the purchase cost of the shading devices but also eliminates the added maintenance costs.

With the use of dynamic glass, internal blinds can also be reduced or totally eliminated. Typical office buildings have some type of interior solar control devices such as mini-blinds or roller shades, the management of which is often left to the user. While considered solar control devices, these devices are primarily used for glare mitigation and privacy. Research has shown that in many cases once the blinds are dropped they remain closed for extended periods of time, limiting the potential to tie the performance of the lighting system to outside conditions. A December 2013 study by the Urban Green Council called Seduced By the View looked at 55 glass buildings in New York and found that on average, 59 percent of the window area was covered by blinds or shades, with more than 75 percent of buildings having more than half of their window area covered regardless of time of day, direction the window faced, and whether the building was commercial or residential. The Council concludes that “New Yorkers are paying for more glass and then pulling down the shades.” This results in excessive interior lighting usage as well as loss of passive solar heat in the winter. Society, too, is paying a price: Windows insulate poorly, waste energy, and cause carbon pollution.

A better solution is an integrated approach in which lighting, HVAC, natural ventilation, and dynamic glass control integrate to offer optimum thermal management. In fact, some designers have gone as far as stating that the façade of a building is actually a component of the HVAC system—a philosophy that is only strengthened by the use of dynamic glass. With such an integrated design approach, other energy-intensive building systems can be reduced and simplified often resulting in little or no additional project cost. Peak loads can be reduced, night flushing can be employed, and material-intensive shading systems can be eliminated. As such, dynamic glass serves as an enabling technology for Net-Zero Energy Project goals. For architects seeking green building certifications, dynamic glass can assist in achieving multiple LEED credits due to benefits such as reduced energy consumption, user controllability, improved thermal comfort, and daylighting. Because dynamic glass touches so many elements of the building's design and operation, it can contribute to eight LEED credit categories and potentially offer between 12-22 points.

To meet aesthetic demands, large, 5 feet by 10 feet dynamic glass units are available. Proprietary advances in coating technology, IGU design and control have enabled large glass units that are active edge-to-edge without internal conductors that interrupt the view, providing the aesthetic, performance, and size needed for the next generation of user-centered, environmentally sensitive buildings. This is an important consideration, as across every building sector, owners are continuously innovating to create landmark environments that emphasize beauty in design, openness and natural light, and a commitment to sustainability and the external environment.

Building Management

In addition to providing the aforementioned optimum energy performance and associated cost savings, dynamic glass systems offer a building manager flexibility. They can be operated in modes from manual only to fully automated and integrated with the building management system. User interfaces are via a wall switch, mobile app, or web interface. The system can be configured to maximize comfort, can be easily zoned and rezoned, and adjusted for weekend settings when the building is unoccupied and there is less need to heat, cool, or prevent glare.

Commissioning is part of a dynamic glass system package. Typically, that package will include commissioning of the control system and intelligence (as installed by a third-party trade). Some manufacturers will evaluate and monitor the systems for a certain period after the initial installation, monitoring log files remotely for performance and soliciting feedback from customers, as well as launching surveys and discussions about the system among building staff. Initially, on-site crews may help with fine-tuning zone controls, refining programming and testing performance of all windows. In an ongoing process the parameters can be adjusted remotely based on changing needs.

Dynamic glass can also contribute to operations savings in other ways, including reduction of fading in interior furnishings and fixtures. Daylight brings in UV radiation which causes fading. When tinted, dynamic glass blocks more than 99 percent of UV rays, increasing the service life of the equipment inside the building.

Dynamic vs Low-E Glass: A Comparison

To demonstrate the potential energy saving benefits for a typical commercial office application, a demonstration site with two identical south-facing perimeter offices in the San Francisco bay area was constructed. One office was installed with traditional low-E glass and the other with EC dynamic glass. Energy monitoring over a period of 12 months resulted in the commercial office room installed with dynamic glass saving a substantial percent of the total energy consumed compared to the office room installed with traditional low-E glass. The offices, located in Milpitas, California, are located on the second floor of a low-rise commercial office building. The two rooms are built with identical office footprints, furniture, and HVAC systems. They are adjacent south-facing perimeter offices and receive the same level of sun exposure. Demonstration Office A was installed with dual pane low-E glass and manual motorized shades. Demonstration Office B was installed with dual-pane dynamic glass. To maintain a controlled environment, both rooms were unoccupied during the duration of the monitoring period. HVAC systems for both rooms are comprised of two dedicated dual duct variable air volume (VAV) boxes that supplied conditioned air to each room. Both systems were tied to a building automation software platform used to control and calculate energy consumption. Dimmable lighting was installed in both rooms with identical lighting set points (25 foot candles). The lighting and HVAC occupancy schedule stayed active from 7am–7pm on weekdays. The HVAC schedule switched to a setback mode during unoccupied periods. Multiple indoor and outdoor sensors were deployed in both rooms to monitor various parameters including illuminance levels, power consumption of equipment, artificial lighting, and indoor temperatures. A proprietary Intelligence control package was implemented into the demo room starting October 2012. The Intelligence package uses geometrical solar penetration (as shown in previous page), radiated energy and real time environmental condition monitoring to automatically change the tint state of the glass for optimal solar control and comfort. The performance assessment reflects 12 months of data collected from October 2012 to September 2013, and is illustrated in the accompanying figure. Average total energy use of low-e vs. dynamic glass Graph courtesy of View Inc. Under glare conditions (which typically relate to high radiation) dynamic glass transitions to the fully tinted state blocking more than 90 percent of the solar heat entering the space, resulting in significant cooling savings. In its fully tinted state, Demonstration Office B required slightly more artificial lighting to maintain desired light levels. However the additional energy required for lighting was negligible compared to the total cooling energy saved. On a summer weekend in August, results reveal significant savings of over 85 percent. Upon further investigation it was determined that this is due to the programming to full tint (max heat rejection)on the weekend. On weekdays, the cooling set point is 73°F, meaning cool air will be supplied to the room once it detects a temperature of 73°F or higher. It is common to raise the setback temperature on weekends due to building vacancy and elimination of the need to cool the area. Hence during the weekend, the setback temperature is set to 82°F. This strategy is commonly employed to save energy in the building, and it does to some extent. However, the dynamic glass’ solar heat gain coefficient keeps the temperature inside the space sufficiently cool so that it scarcely exceeds 82°F during the day, requiring minimal cooling as opposed to low-E glass. The dynamic glass was shown to perform even better in the winter. Heat gain through windows comes in two forms: conductive and radiative. Unlike the summer, radiative heat gain dominates during the winter due to a combination of low sun angle and cooler temperatures. Dynamic glass blocks radiative heat due to its low SHGC values resulting in a higher percentage in savings in the winter as compared to the summer months. Typical perimeter offices in this climate are cooling dominated hence there are very few days when heating is required. Overall, the dynamic glass significantly reduced the cooling load of the space resulting in 39 percent in total energy savings compared to standard low-E glass. Energy monitoring over a period of 12 months resulted in the commercial office room installed with dynamic glass saving 39 percent of the total energy consumed compared to the office room installed with traditional low-e glass. Photos courtesy of View Inc.

 

Building Occupants

In addition to improved daylighting and thermal comfort, dynamic glass allows occupants unobstructed views even in the tinted state, a key to a host of benefits. Dynamic glass is consistent with biophilic design, which seeks to connect humans with the natural environment. The premise is based on the philosophy of biophilia, the apparent instinctive preference humans have for natural geometries, forms, and characteristics within our environments. Studies have shown repeatedly that when access to natural environments is present, even through views, human beings tend to feel calmer, more at ease, more comfortable, less stressed—and their performance, sense of well-being, and even health can improve. Biophilic design is helping to improve productivity in offices, higher scores in schools, and better patient outcomes in hospitals, all with significant fiscal implications. Terrapin Bright Green, an environmental consulting and strategic planning firm committed to improving the human environment through high performance development, policy, and related research, put out a report, The Economics of Biophilia, which is a compilation of studies on the impacts of biophilic design. The report states, “The numbers and percentages presented reflect powerful evidence that many traditional design strategies that ignore nature can lead to negative impacts on human health, child development, community safety, and worker satisfaction. These effects translate directly to increased profits.”

The advantages of biophilic design are evident in all types of buildings. In offices, abundant natural light and expansive views are known to enhance both creativity and productivity. Daylight elevates the spirit and fosters innovative thinking. Large open areas with abundant natural light invite creative collaboration and teamwork among colleagues, all of which seem to make people happier, more optimistic, and get better results. Elzeyadi's study at the University of Oregon, for example, found that 10 percent of employee absences could be attributed to architectural elements that did not connect with nature, and that a person's view was the primary predictor of absenteeism. A 2003 Heschong study found that seating arrangements at the Sacramento Municipal Utility District call center influenced worker performance results. Employees with views of vegetation through large windows handled far more calls per hour than employees with no view of the outdoors.

Methodist Olive Branch Hospital in Mississippi Photo courtesy of View Inc.

Hospitals, too, are using biophilic design to improve patient outcomes. Hospital designers, administration, and staff recognize the benefits of large windows, natural daylight, and expansive outdoor views in speeding recovery. In a groundbreaking 1984 study Ulrich found that patients with a view to nature rather than a mere wall experienced hospital stays that were 8.5 percent shorter, with fewer negative observational comments from nurses, and significantly fewer strong, post-surgical analgesics, according to Terrapin, which states that later reports confirm those findings and demonstrate that “poor design and lack of exposure to nature inhibit recovery rates and blood pressure stabilization, exacerbate anxiety, and increase administration of pain medications.”

Educational facilities too are looking to biophilic solutions to help improve student achievement and reduce operating costs. According to Daylighting in Schools, An Investigation into the Relationship Between Daylighting and Human Performance by the Heschong Mahone Group, the connection between nature and performance is real. Among the group's findings:

• Classrooms with more daylighting are 20 percent faster in math and 26 percent faster in reading.

• Classrooms with larger windows are 15 percent faster in math and 23 percent faster in reading.

• Classrooms with controllable skylights show a 19 to 20 percent improvement in student performance.

• An ample and pleasant view out of a window supports better outcomes of student learning.

• Sources of glare and direct sun penetration into classrooms negatively impact student learning.

• Teachers who can control glare through windows experience improved student performance.

Nearly 20 separate studies have agreed that good daylighting “improves tests scores, reduces off-task behavior, and plays a significant role in the achievement of students” (Kats, 2006). Research also supports the notion that integrating biophilic design into the nation's school system would improve the experience of hundreds of thousands of children, an outcome that may increase the rate of retention, which in itself has implications for the U.S. economy. Some educational facilities have taken that type of thinking to the next level. There is a movement, particularly at the university level, to incorporate biophilic design in order to attract students and professors who are interested in progressive, energy-efficient facilities that lead in environmental consciousness, in reducing carbon footprint, meeting sustainability objectives, and setting an example for the broader community.

Dynamic Glass and Prevailing Standards and Codes

Dynamic glass is being increasingly referenced in the energy codes as distinct from static glass, with California Title 24, the country's most progressive code, taking the lead. Dynamic glass is recognized in Section 140.3 of that code, and also by the 2012 edition of the International Energy Conservation Code (IECC), ASHRAE 90.1 – 2013, the 2015 edition of the International Code Council (ICC) building code, and even the upcoming Energy Star for Windows criteria. As these regulatory agencies update their codes and standards to fully recognize dynamic glazing, architects can use the performance path for dynamic glass to demonstrate lower energy use than the baseline model and exceed code requirements.

LEED v4 has several changes that are impacted by the use of intelligent dynamic glass. There is now a credit category for Integrative Design, which means the consideration of several design scenarios (including alternate façade materials and systems) to get the most efficient total building package. Dynamic glass is an enabling technology in this regard as it impacts multiple systems, providing energy and performance benefits to each. An integrative design approach will uncover these benefits early in the process. This category awards one credit for performing early-stage analysis of energy- and water-related systems.

Second, a major change in LEED v4 is that it now focuses on materials, their material toxicity (termed material transparency) and their total life-cycle impact. Products with a Health Product Declaration that discloses material make up, like some dynamic glass, will earn LEED credits. In addition, the ongoing energy benefits of dynamic glass will reduce the total carbon footprint of a building. Third, LEED v4 is focused on human centered design and performance, taking a serious, increased focus on human health that goes beyond any other building rating system. As the USGBC puts it, “Every story about a green building is a story about people.” This relates directly to the value proposition of dynamic glass and its salutary potential for occupants of all types of buildings.

Crown Opera House Sees Savings in Dynamic Glass

The historic Crown Opera House in New Bremen, Ohio, built in 1895 is undergoing a restoration project that contains high glazing areas. An analysis was conducted to compare dynamic glass versus a baseline glazing package of dual-pane low-e glass with internal motorized shades and exterior sun shades. Dynamic glass was found to reduce peak load cooling by more than 20 percent. HVAC systems are sized by the peak cooling load requirement (cooling needed during the hottest time of the year). By tinting the dynamic glass to 4 percent, the peak load can be reduced allowing for a smaller overall HVAC system. The dynamic glass blocks more than 85 percent of unwanted solar radiation compared to low-E glass, as it automatically adjusts the tint level to block unwanted solar radiation entering the space. The accompanying figure shows the maximum hourly solar radiation entering the space (west facing offices) for the dynamic glass and the baseline glass. With the dynamic glass, the Crown Opera House will realize substantial first time cost savings and annual operating savings with a payback period of 3 years. Dynamic glass versus a baseline glazing package of dual-pane low-e glass with internal motorized shades and exterior sun shades Graph courtesy of View Inc.

 

Meeting California Title 24 Requirements

At California’s Clovis Community Health Center the challenge was to utilize a large glass façade around the center’s foyer that would create a high-technology, state-of-the-art design that meets California’s Title 24 Energy Code. Henderson Architectural Group designed a separate stand-alone building to be the hospital’s eye-stopping showpiece at the front of the hospital’s campus. Some 5,072 square feet of dynamic glass, primarily 5 foot by 10 foot panels, was installed to control solar heat gain around the front entrance of the center, while fulfilling code requirements. The installation met the façade design specifications while matching the high-technology, high-touch design goals with an automated dynamic windows to control daylighting and glare. The glass provides uninterrupted views to the outdoors and a stunning building design at the entrance of the campus. California’s Clovis Community Health Center Photo courtesy of View Inc.

 

Dynamic Glass: A Promising Future

Dynamic glass has significant potential in the emerging world of high-performance green buildings. It not only provides the best energy performance for the building during operation, but also reduces capital cost and material waste in construction while improving occupant comfort and productivity. In addition to allowing greater design freedom to the architectural community, dynamic glass has the potential to positively affect worker productivity through improved thermal and visual comfort as well as connection to the outdoors. Materials such as external and internal shading devices used in the construction or retrofit of buildings can be reduced or eliminated and HVAC equipment and systems downsized. In addition, by limiting heat gain in summer and allowing it in winter, overall energy consumption and associated costs can be decreased. With these advantages, designers and building owners are seeing a clear path to increased specification of dynamic glass.

 

View Inc. is the pioneer in large-scale architectural dynamic glass that intelligently tints and clears in response to external conditions and user preferences, enabling unparalleled control over the amount of light and heat entering a building. www.viewglass.com